Medical devices have been provided for the delivery of material to various portions of the wall forming a vessel of a mammalian body, such as the gastrointestinal tract, to create implants in the wall. See, for example, U.S. Pat. No. 6,251,063. In addition, apparatus for bulking the wall of the esophagus have been provided. See, for example, U.S. Pat. Nos. 6,098,629 and 6,338,345. Apparatus have also been provided for enhancing the repeatability of implant forming procedures. See, for example, U.S. Pat. No. 6,358,197. Radio frequency treatment devices have also been provided. See, for example, U.S. Pat. No. 6,254,598. There remains, however, a need for injection devices that facilitate repeatable injections, as well as other device for treating the tissue in the wall of a mammalian body.